The present invention relates to a cylinder head of an internal combustion engine having a cylinder head housing, a camshaft bearing strip in two parts with a lower part comprising lower bearing blocks and an upper part comprising upper bearing covers plus a rocker cover.
German Patent DE 39 40 845 C1 discloses a cylinder head of an internal combustion engine with a frame-like beam divided into two parts horizontally for camshaft bearing. The lower part of the beam described here has crossbars, each comprising lower parts of the bearing for supporting the intake and exhaust camshaft in which additional struts and supports and receptacles for bucket tappets are arranged between the spaces formed by the crossbars. The upper part of the beam also has crossbars, comprising bearing upper parts corresponding to the bearing lower parts of the lower part for supporting the intake and exhaust camshaft. The upper part of the carrier is also designed to be open toward the upper in the manner of a frame.
With the camshaft carrier according to German Patent DE 39 40 845 C1, the spaces formed between the crossbars are accessible only from above through the upper part of the carrier, e.g., for the introduction of supporting bearings in machining the bearing channels due to the arrangement for accommodating the bucket tappets and the central webs. The upper part of the carrier is necessarily designed to be open at the top so that the arrangement does not provide any protection from splashing oil thrown by the cams during operation of the internal combustion engine and the oil is thrown directly onto the rocker cover, in which case the gaskets between the rocker cover and the cylinder head housing as well as gaskets in the area of the spark plug dome are put under particular stress. In addition, the carrier has only a low resistance torque due to its frame-like design so that there is not adequate rigidity, especially in the longitudinal direction.
The object of the present invention is to improve upon a cylinder head such that an especially great rigidity is achieved in a simple and inexpensive manner, and advantageous production of the camshaft carrier in particular from the standpoint of manufacturing technology is made possible. In addition, the cylinder head should be lightweight and should include only a few parts.
This object is achieved with the features of the present invention, whereby the underlying idea includes a design of the upper part of the camshaft bearing strip which is closed in the manner of a hood, in particular in the area between the bearing covers.
It is especially advantageous here if the camshaft bearing strip comprises integrated oil channels for supplying oil to the camshaft bearing and/or the cams. For example, the oil may be supplied to the oil channels from beneath through the lower part of the camshaft bearing strip in which case channels in the longitudinal direction of the bearing strip convey the lubricant oil to the bearing sites and/or to the cams.
It is regarded as very expedient to manufacture the camshaft bearing strip of a pressure casting of a magnesium alloy and to machine it so that it is at least approximately finished before installation independently of the other components of the cylinder head.
Supporting bearings can be introduced through the lower part from beneath advantageously for machining the bearing channels of the camshaft bearing strip.
According to an especially preferred embodiment of this invention, aluminum screws are provided for fastening the camshaft bearing strip on the cylinder head housing, in particular in an embodiment in which the camshaft bearing strip is made of a magnesium alloy and the cylinder head housing is made of steel and/or aluminum, in which case a particular advantage lies in the low prestress losses of this connection.
It is especially expedient if the joint faces between the camshaft bearing strip and the cylinder head housing and also between the rocker cover and the cylinder head housing are situated in a plane so that finished machining of the cylinder head housing can be performed in one plane.
Preferably a separate camshaft bearing strip is provided for supporting an intake or exhaust camshaft, which thus yields especially structural freedom.
In addition, it is regarded as very advantageous if the spark plug domes for accommodation of the spark plugs are integrally cast in the rocker cover. In comparison with an embodiment with separate pipe connections introduced into the rocker cover for accommodating the spark plugs, this eliminates an additional connection and seal; in comparison with spark plug domes which are cast with the cylinder head housing, this yields the advantage that an embodiment together with the rocker cover in a magnesium alloy is possible.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.